Hydrostatic and chemical pressure tuning of CeFeAs$_{1-x}$P$_x$O single crystals: The intriguing interaction between 3$d$- and 4$f$-correlations

We present a combined P-substitution and hydrostatic pressure study on CeFeAs$_{1-x}$P$_{x}$O single crystals in order to investigate the peculiar relationship of the local moment magnetism of Ce, the ordering of itinerant Fe moments, and their connection with the occurrence of superconductivity [1,2]. Our results evidence a close relationship between the weakening of Fe magnetism and the change from antiferromagnetic to ferromagnetic ordering of Ce moments at $p^*=1.95$ GPa in CeFeAs$_{0.78}$P$_{0.22}$O. The absence of superconductivity in CeFeAs$_{0.78}$P$_{0.22}$O and the presence of a narrow and strongly pressure sensitive superconducting phase in CeFeAs$_{0.70}$P$_{0.30}$O and CeFeAs$_{0.65}$P$_{0.35}$O indicate the detrimental effect of the Ce magnetism on superconductivity in P-substituted CeFeAsO.\\[4pt] [1] A. Jesche, T. F\"orster, J. Spehling, M. Nicklas, M. de Souza, R. Gumeniuk, H. Luetkens, T. Goltz, C. Krellner, M. Lang, J. Sichelschmidt, H.-H. Klauss, and C. Geibel, Phys. Rev. B 86, 020501(R) (2012).\\[0pt] [2] K. Mydeen, E. Lengyel, A. Jesche, C. Geibel, and M. Nicklas, Phys. Rev. B 86, 134523 (2012).